The emerging field of quantum information has applications in communication, sensing, metrology, cryptography, and computing among others. However, these applications often require the on-demand generation of a single photon having a given frequency and polarization. For many quantum information applications, it is necessary to generate a single photon with a given wavelength that can arrive at a particular location at a particular time. This requires a source that can generate a single photon of a given wavelength on demand.
Some approaches for generating single photons are described in Pittman et al., “Single photons on pseudo-demand from stored parametric downconversion,” Phys. Rev. A 66:042303 (2002), Kok et al., “Linear optical quantum computing with photonic qubits,” Rev. Mod. Phys. 79, 135 (2007), Joshi et al., “Frequency multiplexing for quasi-deterministic heralded single-photon sources,” arXiv:1707.00048 (2017), Jeffrey et al., “Towards a periodic deterministic source of arbitrary single-photon states,” New Journal of Physics 6, 100 (2004), and Migdall et al., “Tailoring single-photon and multiphoton probabilities of a single-photon on-demand source,” Phys. Rev. A 66:053805 (2002). Some approaches use switches that select an optical path associated with a selected output photon frequency. Unfortunately, switches can be lossy, and the signal photon can be absorbed or otherwise lost due to the switch (or other components) and thus no suitable output photon becomes available. In addition to their unreliability in producing a desired photon on demand, systems using multiple optical paths and multiple pump sources (such as described in Joshi) tend to be complex and expensive. Accordingly, improved approaches are needed.